BDNF and atrial fibrillation: In this study, we hypothesised that the human AF and NP cells exhibit different responses to pro-inflammatory cytokines IL-1β or soluble factors derived from ECs, respectively With regard to the interactions between each IVD cell and the ECs, we investigated the effects of potential contributing factors, including inflammatory mediators and catabolic enzymes derived from IL-1β-stimulated IVD cells on ECs and vice versa, in order to explore the development of IVD degeneration through the secretion of inflammatory mediators and neurotrophins.